From mboxrd@z Thu Jan 1 00:00:00 1970 From: james.morse@arm.com (James Morse) Date: Fri, 02 Sep 2016 11:56:39 +0100 Subject: [PATCH V2] arm64:ftrace: add save_stack_trace_regs() In-Reply-To: <57C95967.9030308@arm.com> References: <4f7d7a6bff7f06f814bf9a2bdc90bb0e3b833b66.1472734699.git.panand@redhat.com> <57C95967.9030308@arm.com> Message-ID: <57C95AE7.5030104@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 02/09/16 11:50, James Morse wrote: > Hi Pratyush, > > On 01/09/16 14:35, Pratyush Anand wrote: >> Implement save_stack_trace_regs, so that stacktrace of a kprobe events can be >> obtained. > > Hmm, kconfig enables 'CONFIG_KPROBE_EVENT' if we select KPROBES and FTRACE, this > calls save_stack_trace_regs(), which we haven't implemented, giving: > [ 373.406982] save_stack_trace_regs() not implemented yet. > [ 373.413020] ------------[ cut here ]------------ > [ 373.417601] WARNING: CPU: 1 PID: 0 at ../kernel/stacktrace.c:74 save_stack_tr > ace_regs+0x3c/0x48 > [ 373.426212] Modules linked in: > [ 373.429238] > [ 373.430716] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.8.0-rc4-dirty #5128 > [ 373.437606] Hardware name: ARM Juno development board (r1) (DT) > [ 373.443466] task: ffff800975dd1900 task.stack: ffff800975ddc000 > [ 373.449327] PC is at save_stack_trace_regs+0x3c/0x48 > [ 373.454242] LR is at save_stack_trace_regs+0x3c/0x48 > [ 373.459156] pc : [] lr : [] pstate: 600003c5 > [ 373.466476] sp : ffff80097ef52c00 > > [ 373.554836] Call trace: > [ 373.641153] [] save_stack_trace_regs+0x3c/0x48 > [ 373.647104] [] __ftrace_trace_stack+0x168/0x208 > [ 373.653138] [] trace_buffer_unlock_commit_regs+0x5c/0x7c > [ 373.659946] [] kprobe_trace_func+0x308/0x3d8 > [ 373.665721] [] kprobe_dispatcher+0x58/0x60 > [ 373.671327] [] kprobe_breakpoint_handler+0xbc/0x18c > [ 373.677705] [] brk_handler+0x50/0x90 > [ 373.682792] [] do_debug_exception+0x50/0xbc > > > I guess hitting a WARN_ONCE() while using a 'kernel hacking' feature isn't > serious enough to make this a fix. > I wasn't clear enough with the above: this patch is fixing this WARN_ON(), it may be worth mentioning that in the commit message... Thanks, James